1. Field of the Invention
The present invention relates to a process for separating nickel and cobalt from a sulfide material containing the same and recovering such values with minimal losses thereof.
2. Description of the Prior Art
Nickel ores generally contain a small amount of cobalt. In fact, low grade nickel ores sometimes contain up to one-tenth as much cobalt as nickel. These materials are separately by a sulfurizing process in the hydrometallurgical process and it is known that cobalt precipitated during the refining process from a solution containing nickel by the use of a sulfurizing agent or the like will generally contain co-precipitated nickel. It is also known that high purity metallic nickel and nickel compounds may be produced by subjecting the precipitated cobalt values to a series of precipitation steps and recycling as much nickel as possible back to the initial refining process. This repetition of cobalt precipitation steps causes an accumulation of cobalt in the precipitates separated from the solution containing nickel and some process is required for separating and recovering nickel and cobalt from the mixture thereof thus produced and for removing impurities such as iron, copper, zinc and manganese therefrom.
When roasted at 900.degree.-950.degree. C in the presence of oxygen, a mixture of nickel and cobalt sulfides may be stripped of combustibles and volatiles and converted into oxides which are soluble in hydrochloric acid. However, it is to be recognized that the solubility of the roasted product in hydrochloric acid decreases as the roasting temperature rises above 1000.degree. C while the removal of sulfur impurities and the like is incomplete at roasting temperatures less than 900.degree. C. In either event, the electrolysis of the nickel chloride using insoluble anodes is adversely affected.
It is known that if the nickel content of the roasted product comprises at least 20 percent by weight of the total nickel and cobalt content, almost all of the cobalt as well as all of the nickel in the mixed material may be dissolved in hydrochloric acid. The aqueous solutions containing chlorides of cobalt and nickel thus obtained generally also contains impurities such as iron, chromium, antimony, arsenic, copper, zinc and manganese which, in previously known processes, is removed prior to the separation of cobalt and nickel. After the removal of impurities, the remaining solution is then subjected to solvent extraction using a triamine such as trinormaloctylamine (TNOA) or triisooctylamine (TIOA) in a manner well known to those skilled in this art whereby the cobalt complexes with the triamine to form a complex salt having the formula (R.sub.3 NH).sub.2 CoCl.sub.4. This complex cobalt salt is dissolved in the triamine solvent while the nickel chloride remains in the aqueous solution and accordingly nickel and cobalt are separated. The cobalt extracted in the triamine solvent is then stripped with water to produce an aqueous solution containing purified cobalt from which metallic cobalt and cobalt compounds may be obtained. Likewise, metallic nickel and nickel compounds may be obtained from the nickel chloride solution.
The conventional processes discussed above require the substantially complete removal of impurities prior to the separation of nickel and cobalt, and, as a result, a certain amount of nickel and cobalt is removed with the impurities and is lost. Thus, yields are decreased.